DNA testing of a descendant of Elkanah's has conclusively matched Elkanah Briggs as a descendant of Clement Briggs of Plymouth MA. Clement Briggs arrived in the Plymouth Colony on the ship "Fortune" in 1621. He was a "felmonger" from Southward of Surrey, England. His sons lived in Taunton MA.
The first record of Elkanah Briggs I have found places him in GA in 1794. He would have been about 28 years old.
Elkanah Briggs is on a list of "The Whole of Inhabitants Being as Follows" in Camden Co. GA. I believe that this is in 1794 based on the preceeding record containing names of jurors from the Book of Interior Court Records 1794. Of the 36 names on the list of jurors, 34 are also on the list of Inhabitants. [Historical Collections of the Joseph Habersham Chapter Daughters of the American Revolution, Vol. III, 1910] Camden is in the far southern coastal area of the state. In about 1821 a Cyrus Briggs married Margaret Ludworth in Camden co. GA. [same source]
Son Jacob Briggs in the 1880 St. Clair county AL census states that his father was born in Massachusetts and mother in Virginia.In the 1900 census Nancy Briggs, daughter of Micah Briggs, gave MA as the birth state of her father. Grandson David N. Briggs, son of Eli N. Briggs, gave his father's birth state as “Massachat" in the 1930 census. The parents of these two grandchildren were actually born in GA but I suspect that they had heard stories of their family origins in Mass.
So, now the task is tracing Elkanah through the missing generations to Clement Briggs.